Oxo catalyst removal process



July 31, 1956 T. G. JONES ETAL 0x0 CATALYST REMOVAL PROCESS 2 Sheets-Sheet 1 Filed Sept. 8. 1952 a a. q a m i 8 M a 1+ Q 7 p 6 Q 9 w Q a A 5* can W G PM/ Q 2 U 2 4 M 0. \J x NU. O Q l I HS WI! c I: Hw 8 V32 1 .1 C .1 ll :1 2 Q 0 1 vi a A E Q 6 o 3 v 8 CA W a A E Q 1:IG.- i

g eiz l-ia g g firm/enters acb G. Fuquq Qbtiorneg United States Patent 0X0 CATALYST REMOVAL PROCESS Thomas G. Jones, Glen P. Hamner, and Mack C. Fuqna,

Baton Rouge, La., assignors to Esso Research and Engineering Company, a corporation of Delaware Application September 8, 1952, Serial No. 308,354

7 Claims. (Cl. 260-604) The present invention relates to the preparation of organic compounds by the reaction of carbon monoxide and hydrogen with carbon compounds containing olefinic linkages in the presence of a carbonylation catalyst. More specifically, the present invention relates to the removal and recovery of the cobalt catalyst utilized in the foregoing reaction from the product of the first stage of the cobalt carbonylation reaction for further use in the process.

It is now well known in the art that oxygenated organic compounds may be synthesized from organic compounds containing olefinic linkages by a reaction with carbon monoxide and hydrogen in the presence of a catalyst containing metals of the iron group, such as oobalt or iron, preferably the former, in an essentially threestage process. In the first stage, the olefinic material, catalyst and the proper proportions of CO and H2 are reacted to give a product consisting predominantly of aldehydes containing one more carbon atom than the reacted olefin. This oxygenated organic mixture, which contains dissolved in it salts and the carbonyls and mo lecular complexes of the metal catalyst, is treated in a second stage to cause removal of soluble metal compounds from the organic material in a catalyst removal zone. The catalyst-free material is then generally hydrogenated to the corresponding alcohols, or may be oxidized to the corresponding acid.

This carbonylation reaction provides a particularly attractive method for preparing valuable primary alcohols which find large markets, particularly as intermediates for plasticizers, detergents and solvents. Amenable to the reaction are long and short chained olefinic compounds, depending upon the type alcohols desired. Not only olefins, but most organic compounds possessing at least one non-aromatic carbon-carbon double bond may be reacted by this method. Thus, straight and branch chained olefins and di-olefins such as propylene, butylene, pentene, hexene, heptene, butadiene, pentadiene, styrene, olefin polymers such as diand tri-isobutylene and hexene and heptene dimers, polypropylene, olefinic fractions from the hydrocarbon synthesis process, thermal or catalytic cracking operations, and other sources of hydrocarbon fractions containing olefins of 3 to 14 carbon atoms may be used as starting material, depending upon the nature of the final product desired.

The catalyst in the first stage .of the prior art processes is usually added in the form of salts of the catalytically active metal with high molecular weight fatty acids, such as stearic, oleic, palmitic, naphthenic, etc., acids. Thus, suitable catalysts are, for example, cobalt oleate or naphthenate, or linoleate. These salts are soluble in the liquid olefin feed and may be supplied to the first stage as hydrocarbon solution or dissolved in the olefin feed.

The synthesis gas mixture fed to the first stage may 2,757,206 Patented July 31, 1956 "ice consist of any ratio of Hz to CO, but preferably these gases are present in about equal volumes. The conditions for reacting olefins with H2 and CO vary somewhat in accordance with the nature of the olefin feed, but the reaction is generally conducted at pressures in the range of about 1500 to 4500 p. s. i. g. and at temperatures in the range of about 150-450 F. The ratio of synthesis gas to olefin feed may vary widely; in general, about 2500 to 15,000 cubic feet of H2+CO per barrel of olefin feed are employed.

At the end of the first stage, when the desired conversion of olefins to oxygenated compounds has been effected, the product and the unreacted material are generally withdrawn to a catalyst removal zone, where dissolved catalyst is removed from the mixture and it is to this stage that the present principal invention applies.

From the catalyst removal zone the reaction products, comprising essentially aldehydes, may be transferred to a hydrogenation zone, and the products reduced to the corresponding alcohols in a manner known per se.

One of the problems involved in the aldehyde synthesis reaction is the fact that the catalyst metal, such as cobalt, though added as an organic salt, reacts with carbon monoxide under the synthesis conditions to form the metal carbonyl. There is basis for the belief that the metal carbonyl itself is the active form of the catalyst. This dissolved catalyst must be removed prior to the subsequent hydrogenation, as otherwise it would separate out on the hydrogenation catalyst, plug transfer lines and heat exchangers, etc. The carbonyl remains dissolved in the reaction product from the primary carbonylation stage and is therefore removed in the catalyst removal, or decobalting zone. One way to remove the cobalt is by a thermal method wherein the accrued product in the first stage is heated to a temperature of from about 300-350 F. Conveniently, a steam coil immersed in the liquid to be decobalted is employed. A pressure of from about -175 p. s. i. g. is maintained in the decobalting zone by the injection of a gasiform material such as hydrogen, an inert vapor, etc. It is desirable to employ a gasiform material in order that the CO partial pressure he maintained at a relatively low value in the decobalting zone. Periodically it is necessary to take the decobalter olf stream to remove accumulated metallic cobalt to prevent plugging of the feed lines and adjacent areas of the decobalting vessel. Furthermore, cobalt metal deposits as a film on the heating means and requires constant removal to prevent plugging of the preheating equipment and surfaces. The removal of these films and deposited cobalt metal is a tedious and diflicult process and adds a significant cost to the economics of the carbonylation reaction. Furthermore, thermal decobalting usually did not completely remove soluble cobalt from the aldehyde product.

It is one of the purposes of the present invention to provide an improved and novel means for removing dissolved carbonylation catalyst from conversion products resulting from the reaction of olefinic compounds with carbon monoxide and hydrogen.

It is also a purpose of the present invention to describe an eflicient and effective means for recovering and reutilizing carbonylation catalyst.

Other and further objects and advantages of the invention will become apparent from the more detailed description hereinafter.

It has now been found that when the reactor efiluent from the carbonylation zone is treated with dilute aqueter soluble and oil insoluble, exceptionally efiicient dea; cobalting is obtained with residual cobalt content of the aldehyde product consistently less than 50 parts per million and usually about 1050 parts per million. The thermal decobalting process frequently left a feed for the subsequent hydrogenation process containing from 100-500 parts per million .of dissolved cobalt material. This resulted from the fact that though cobalt carbonyl is readily decomposed at the thermal conditions, other compounds of cobalt, such as cobalt salts, are quite stable at these temperatures. Cobalt salts originate from the formation of secondary reaction products, such as formic and higher fatty acids in the course of the reaction, and from the fatty acid cobalt soaps originally added as catalyst.

In accordance with the invention, therefore, the aldehyde synthesis product containing about 1800-2000 parts per million or more of cobalt, is treated with dilute aqueous organic acid at temperatures substantially below those required for thermal decobalting, in the range of about 150 to 200 F. In view of the heat-sensitive nature of the aldehyde, substantial secondary reaction product formation is thus avoided.

The decobalting temperature of the present invention is critical, and must be kept within the above limits, and preferably within the even narrower limits of 160 to 185 F. Above about 190 F., thermal decomposition instead of the desired chemical reaction becomes the dominant reaction, thus precipitating metallic cobalt, which has the tendency to deposit and plate out on hot surfaces, such as coils and tubes, eventually fouling them and thus requiring shutdowns for cleaning. On the other hand, decobalting temperatures less than about 150 F. are too low for adequate chemical cobalt removal, thus requiring excessive periods of time for the completion of the removal, and causing lengthy product and process hold-ups. This temperature effect may be illustrated by the data below:

EFFECT OF TEMPERATURE ON DECOBALTING The original aldehyde product from the x0 stage, upon which the above tests were performed, contained 1660 parts per million of cobalt.

The process of the present invention is particularly effectively operated when the acid decobalting step is followed by a treatment of the aldehyde product with hot water and/or steam. Such process has been found to produce, even in continuous commercial operation, an aldehyde product feed for the subsequent hydrogenation stage containing one part or less of cobalt per million. This combination acid-treating and hot water/steam treating of aldehyde product has for the first time produced a hydrogenation feed that does not foul the catalyst or the equipment in the hydrogenation zone.

An important advantage of the present invention is that in accordance therewith, cobalt recovery is considerably simplified and made more feasible. Because of the importance of this metal, it is essential for an economically feasible process that substantially all the metal be recovered and re-utilized. This is readily done in accordance with the present invention. Thus instead of precipitating the metal as a solid as in prior art processes, the effect of dilute aqueous organic acid injection is to convert substantially all the cobalt, regardless in What form it is present in the aldehyde product, into the corresponding water soluble salt. In one embodiment of the inven tion, this water soluble salt may be recycled directly to the aldehyde synthesis zone to provide both catalyst and cooling for said zone. In another embodiment, the salt may be neutralized to form the hydroxide, suspended in an organic liquid, like aldehyde product or olefin, and recycled to the reaction zone. This is carried out when it is desired to avoid excessive addition of water to the carbonylation zone. If desired, the recovered water soluble cobalt salt may be heated with a higher molecular weight organic acid to form an oil soluble cobalt salt.

The present invention will best be understood from the more detailed description hereinafter, wherein reference will be made to the accompanying drawings, which is a schematic representation of a system suitable for carrying out a preferred embodiment of the invention.

Turning now to the figure, olefin feed is passed, after preheating in a fired coil (not shown) through feed line 4 to the bottom portion of primary reactor 2. The latter comprises a reaction vessel which may, if desired, be packed with non-catalytic material, such as Raschig rings, pumice, and the like, and may be divided into discrete packed zones.

Catalyst may be injected into the olefin feed in one modification of the invention, as an oil-soluble cobalt soap, such as cobalt oleate or naphthenate or the like, through line 6 in amounts equivalent to about 0.1-0.5 of cobalt on olefin. This cobalt oleate may be produced from the water soluble cobalt salt resulting from the decobalting operation. In another modification of the inven tion, an aqueous solution of an organic cobalt salt is introduced through line 8 into reactor 2.

Simultaneously, a gas mixture comprising preferably approximately equal volumes of H2 and CO is supplied through line 3 to primary reactor 2 and flows concurrently with the olefin feed. Reactor 2 is preferably operated at a pressure of about 2500-3500 p. s. i. g. and at a temperature of about 200-450 5., depending upon the olefin feed and other reaction conditions.

Liquid oxygenated reaction product containing catalyst in solution and unreacted synthesis gas, are withdrawn overhead from an upper portion of reactor 2, and transferred through line 10 and cooler 12 to high pressure separator 14, where unreacted gases are withdrawn overhead through line 17 and preferably at least in part recycled.

A stream of primary reaction product containing dis solved therein relatively high concentration of cobalt carbonyl and other forms of cobalt is withdrawn from separator 14 through line 16. A portion of this stream may be recycled, if desired, to reactor 2 via line 18 to aid in cooling and maintenance of temperature control of the primary carbonylation stage. The balance of the primary reaction product may be Withdrawn through pressure release valve 20 and transferred through line 22 to low pressure separator 24, wherein de-gassing is substantially completed. The latter vessel may be at a pressure of about 25 to 200 p. s. i. g.

Degassed aldehyde product is passed from the lower portion of 24 through line 26 to mixer 28. This unit is of any conventional design, and is adapted to mix thoroughly an aqueous and a water-insoluble liquid organic phase. Water is injected through line 29 and an organic acid whose cobalt salts are water soluble is added through line 31. Suitable acids are acetic, formic, and the like. Acetic acid is preferred, for its cobalt salts have greater water solubility, thus requiring less water for their complete recovery. Acid is added in amounts suificient at least to combine with all the cobalt present, and water is added in amounts at least sufficient to dissolve all the cobalt salt formed. Thus, a satisfactory operation may be had employing about 10% (based on aldehyde) of a 5% aqueous solution of acetic acid. For less water soluble cobalt salts, a greater amount of water is required.

ars /320a The temperature level within mixer 28 must be carefully controlled. Higher temperatures speed the reaction rate, but too high temperatures result in thermal decomposition of cobalt carbonyl to metallic cobalt, which is diflicultly soluble in the dilute acid mixture, and this is undesirable. The temperature within mixing zone 28 is preferably maintained at about 150 to 185 F. and should not, under any circumstances, exceed 200 F.

After a sufilcient mixing period, on the order of 30 to 120 minutes, more or less, the mixture is passed through line 30 to settler 32, where the aqueous and aldehyde layers are allowed to stratify. The upper aldehyde layer may then be passed to water washing equipment, where hot water, say at about 165 F., may be injected through line 36 to Wash out the last traces of cobalt acetate and acetic acid. About 10% of water on the aldehyde product may be used for this purpose and the wash water, withdrawn through line 38, may be advantageously employed as the diluent for the organic acid used as the decobalting medium. The aldehyde product may then be given a second water wash in 40 with an excess of cold water, say about 200%, to remove any traces of organic acid.

The aldehyde stream, which has now been reduced in cobalt content from about 2000 parts per million to 10- parts per million, is now advantageously passed to heating vessel 54 through line 52. A stream of water is concomitantly injected through line 56; the water may be from any source, and if desired, may comprise or consist of the waste wash water from previous operation. It is advantageous for realization of complete decobalting that the heating vessel 54 be substantially completely filled with the mixture of water and aldehyde product. Temperatures of about 250 to 350 F. and pressures of 100 to 200 p. s. i. g. are maintained within vessel 54. Inthe diagram only one heater vessel is shown; if desired, two or three vessels operating in series or parallel may be employed. The flow is preferably upstream, and a residence time of 15 to 60 minutes is maintained to achieve substantially complete removal of dissolved cobalt from the aldehyde product.

The mixture is withdrawn from 54 through line and passed to settling vessel 58, which is provided with bafiles to prevent mixing and also with a conical bottom to facilitate settling. In 58 the mixture is allowed to stratify and the vessel serves to settle suspended solids, to stratify immiscible organic and aqueous phases, and to disengage vapors. Overhead from vessel 58 are Withdrawn offgases, which may be sent to the burner system. The upper aldehyde layer, containing in solution less than 5 parts per million of cobalt, and usually one part per million I or less, is withdrawn through line 60, cooled and, if desired, filtered and passed to the hydrogenation zone for conversion to alcohols, or processed in any desired manner. From the lower portion of 58, an aqueous stream containing solid particles of cobalt is withdrawn through line 62. If desired, this cobalt may be recovered, though usually it is in an amount too small for practicable recovery.

Returning now to settler 32, the lower aqueous layer containing in solution the recovered cobalt salt is Withdrawn through line 44. When it is desired to return the cobalt as an oil-soluble salt, rather than as the water-soluble salt, the aqueous stream may be passed through line 46 to reactor 48, wherein a high molecular weight organic acid such as oleic acid may be added. The recovered salt may be heated with acetic acid until the acetic acid is driven off overhead and the oil-soluble salt formed, which is then recycled to the reactor 2 via lines 50, 6 and 4, preferably dissolved in olefin feed.

Another method of recovering the cobalt as a fatty acid salt is to treat the cobalt acetate with the olefin to be concompleteness of the cobalt recovery and the facility in handling the recovered cobalt. The latter, in the form of the water soluble salt, may thus be returned directly to reactor 2 via lines 44 and 8; precautions must be taken not to flood the reactor with water. Thus, the amount of water added to reactor 2 should not be substantially above 3 to 5% of the olefin added to the reactor. The tolerance of the mixture in the upper portion of reactor 2 for Water is considerably greater than in the lower portion, due to the fact that the aldehyde concentration in the upper part of zone 2 is much greater than in the lower portion. In the embodiment wherein an aqueous solution of cobalt salt is recycled to the aldehyde reactor, it may be desirable to preheat this stream to reaction temperature. It may, however, under some circumstances, be advantageous to add this aqueous stream at a substantially lower temperature level than that obaining in the reactor, to provide at least a part of the cooling requirements. This would allow the aldehyde recycle cooling stream through 18 to be diminished, thus adding to the overall capacity of the reaction system and cut down the time that aldehydes are exposed to high temperatures.

Still another way of returning catalyst to the reaction zone is to neutralize the aqueous stream and form a solid cobalt material. This is advantageous when it is desired to avoid recycling water, and is somewhat cheaper than reconversion to the high molecular weight fatty acid soap. Thus, the water layer may be neutralized with a suitable base, as NaOH, and the cobalt converted to the hydroxide. The water containing the suspended cobalt hydroxide may be contacted by a small amount of aldehyde product which preferentially wets the solid, causing it to be concentrated in a small volume. The cobalt hydroxide may then be recycled to the aldehyde synthesis stage. or may be used for preparing oil soluble catalyst. Other materials, such as hydrocarbons, water-insoluble alcohols, etc., may also be used as the flotation medium. Likewise, the slurry of cobalt hydroxide may be filtered, and the precipitate suspended as a slurry in aldehyde or olefin feed for recycle to the aldehyde synthesis zone.

The invention admits of numerous modifications apparent to those skilled in the art. Thus, it may be desirable in an existing conventional thermal decobalting type plant to add an auxiliary organic acid washing system to remove the last traces of cobalt generally still found in thermal decobalter effiuent. Thus, after a typical thermal decobalting operation, the effluent and feed to the hydrogenation zone, still contained 0.0046% cobalt. After treatment with 0.2% formic acid, the cobalt content was reduced to 0.0003%.

Other modifications obvious to those skilled in the art are within the spirit of the invention.

The invention may be further illustrated by the following specific examples of laboratory and plant tests employing organic acid decobalting.

It may, under some circumstances, be desirable to employ a dilute solution of an inorganic acid for decobalting, such as HCl or H2804. However, it is generally not desirable to recycle the salts thus recovered to the synthesis reactor, because of the possible decomposition products resulting from the subjection of halides and sulfates to aldehyde synthesis conditions of pressure and temperature, particularly in the presence of CO and H2.

Example I A batch decobalting test was made in plant scale equipment by mixing 10 volume percent of a 2.4% strength formic acid with undecobalted Oxo aldhehyde containing 950 p. p. In. total cobalt. After mixing, the temperature was gradually raised to F. at atmospheric pressure. Results of the test showed that good decobalting was obtained after 30 minutes at 185 F., when the aldehyde layer, after centrifuging and filtering, contained only 8 p. p. m. soluble cobalt. The water layer at the "7 end of 'the test contained 9400 p. p. in total cobalt, and 0.75% free formic acid.

Example II A continuous plant scale decobalting test with formic acid solution was conducted on de-gassed OX aldehyde product containing ll401570 p. p. m. total cobalt, using vol. percent water and 0.25 vol. percent formic acid on aldehyde. Reaction was carried out in a mixing drum at 175-185 R, 10 p. s. i. g. pressure, with 2% hours hold-up time, followed by settling, removal of the waterformic acid-cobalt layer, then an additional water wash as the aldehyde was pumped to storage tanks. The soluble cobalt content of the aldehyde layer decreased to an Feed.- Undecobalted aldehyde containing 1800 p. p. In. total cobalt 100 vol. percent H20 and 2 vol. percent formic acid on aldehyde.

LABORATORY DATA SHOWING USE OF ACETIC ACID Feed.Undecobalted aldehyde containing approximately 1800 p. p. m. total cobalt. average of 98 p. p. m. at the llllXlIlg drum outlet, 44 p. p. h m. at the settler outlet, 21 p. p. m. after the final water l 10 Percent H and P wash, and 2 p. p. m. after settling in the final storage acellc a C1d 011 aldehyde- 0 tanks for about 2 days. The water-acid layer as re- Tl'eatlng t1me 1O mlmltes M185 moved from the settler contained 7950 p. p. m. total 20 Soluble l P- P- cobalt- LABORATORY DATA COMPARING WATER WASHING VS.

Example III ACID WASHING OF THERMALLY DECOBALTED ALDE- HYDE PRODUCT LABORATORY TEST DATA.REUSE OF COBALT FROM FORMIC ACID SOLUTION Feed.Aldehyde product from 100 B./D. plant ther- Aldehyde synthesis stagcrcaetiou AuftoclagctmitatiOOOpsg.350F. mally decobalted at 300350 F. With hydrogen, COH- or5 oursover11I-I O as. g n 07 01cm 2/ g taming 75 p. p. m. cobalt.

atal st Wt l t t 1 1t y di ital? as ie igv d ii oig ilyo Washed w th water only65 p. p. m. cobalt.

J nlantdecobaltef- Washed with formic acid solutionless than 1 p. p. 111. Water cone. vol. percent on olefin Cobalt, \vt. percent 01101 11 ,1 cobalt after freezing out emulsion. Olefin conversion, pcrcent 80.

That acetic acid gives as effective decobalting as formic Similar data have been obtained on use of cobalt acetate. acid is shown in the following data, wherein both the The above data clearly show that the recovered aldehyde product taken directly from the carbonylation aqueous solution of cobalt salt is highly suitable as catstage, and the aldehyde product after conventional theralyst for the aldehyde synthesis reaction. mal decobalting, are subjected to acetic acid treatment.

Vol. Por- V01. Icr- Temp, Sample Acid cent Acid cent H10 F. of Time, Cobalt, on Alde- 0n Alde- Wash Min. p. p. m.

hyde yde ()xo Prod 0.5 180-190 30 1 Thermally decobaltod 0.1 10 180-190 30 1 product. OX0 Product 0.25 5 170 30 3 Thermally deeobaltcd 0.036 10 180-100 30 1 product.

LABORATORY DATA ON USE OF FORMIC ACID AFTER Wh t i l i d i THERMAL DECOBALTING 1. In a continuous carbonylation process wherein car- F d was thermally dccobalted aldehyde containing bon compounds containing olefinic double bonds are con- 112 P total Cobalt 200 treat. 50 tacted in a carbonylation reaction zone with CO and H2 in the presence of a cobalt carbonylation catalyst under V01 WP V0] PM; semmp OIldiliOns to produce reaction products comprising aldecent. Bio eoutForinit': Treating Cobalt in hydes containing at least one more carbon atom than 3. t g TlmeiMmsaid carbon compounds, wherein carbonylation catalyst metal compounds are dissolved 111 said reaction prod- 5 m 5 nets, and the solution comprising said reaction products 10 0. 003 15 5 and the therein dissolved catalyst metal compounds is transferred to a catalyst removal zone, the improvement ernpm'a- Soluble C()- Agitation 'lime, Min. turn, l ball; in Product, p. p. In.

which comprises treating said contaminated aldehyde product in said last named zone with an aqueous solution of an organic acid whose cobalt salts are aldehydeinsoluble and at least moderately water soluble at a temperature above about 150 F. and below about 190 F. passing the resulting mixture of aldehyde product and aqueous acid solution from said catalyst removal zone to a first settling Zone, Withdrawing an aldehyde product substantially reduced in cobalt from said first settling zone, passing said aldehyde product to a heating zone, passing liquid water to said heating zone, maintaining a temperature of from about 250350 F. in said heating zone, passing aldehyde product and an aqueous phase from said heating zone to a second settling zone, and withdrawing an aldehyde product substantially completely free from dissolved cobalt from said second settling zone.

2. In a continuous carbonylation process wherein an olefin of 3 to 14 carbon atoms is contacted in an aldehyde synthesis reaction zone with CO and H2 and a cobalt catalyst at elevated temperatures and pressures to produce an aldehyde product and wherein cobalt-contaminated aldehyde product is transferred to a catalyst re moval zone, the improvement which comprises passing said aldehyde product into a mixing zone, injecting into said zone an aqueous solution of an organic acid whose cobalt salts are at least moderately water soluble, maintaining a temperature of from about 160-185 F. in said zone, passing said mixture to a settling zone, withdrawing an aldehyde product substantially reduced in cobalt from said zone, passing said aldehyde product to a heating zone, passing liquid water to said zone, maintaining a temperature of from about 250350 F. in said zone, passing aldehyde product and an aqueous phase from said last named zone to a settling zone, and withdrawing an aldehyde product substantially completely free from dissolved cobalt from said last named zone.

3. The process of claim 2 wherein water is the continu ous phase in said heating zone.

4. The process of claim 2 wherein water is added to said heating zone at atmospheric temperatures.

5. The process of claim 2 wherein said acid is acetic acid.

6. The process of claim 2 wherein cobalt is recovered from the aqueous solution withdrawn from said first named settling zone.

7. The process of claim 2 wherein cobalt-containing aqueous solution withdrawn from said first named settling zone is passed to said aldehyde synthesis zone to furnish at least a portion of the catalytic requirements of said zone.

References Cited in the file of this patent UNITED STATES PATENTS 2,596,920 Smith et al. May 13, 1952 2,638,487 Russum et al. May 12, 1953 FOREIGN PATENTS 493,493 Belgium Feb. 15, 1950 

1. IN A CONTINUOUS CARBONYLATION PROCESS WHEREIN CARBON COMPOUNDS CONTAINING OLEFINIC DOUBLE BONDS ARE CONTACTED IN A CARBONYLATION REACTION ZONE WITH CO AND H2 IN THE PRESENCE OF A COBALT CARBONYLATION CATALYST UNDER CONDITIONS TO PRODUCE REACTION PRODUCTS COMPRISING ALDEHYDES CONTAINING AT LEAST ONE MORE CARBON ATOM THAN SAID CARBON COMPOUNDS, AND WHEREIN CARBONYLATION CATALYST METAL COMPOUNDS ARE DISSOLVED IN SAID REACTION PRODUCTS, AND THE SOLUTION COMPRISING SAID REACTION PRODUCTS AND THE THEREIN DISSOLVED CATALYST METAL COMPOUNDS IS TRANSFERRED TO A CATALYST REMOVAL ZONE, THE IMPROVEMENT WHICH COMPRISES TREATING SAID CONTAMINATED ALDEHYDE PRODUCT IN SAID LAST NAMED ZONE WITH AN AQUEOUS SOLUTION OF AN ORGANIC ACID WHOSE COBALT SALTS ARE ALDEHYDEINSOLUBLE AND AT LEAST MODERATELY WATER SOLUBLE AT A TEMPERATURE ABOVE ABOUT 150* F. AND BELOW ABOUT 190* F. PASSING THE RESULTING MIXTURE OF ALDEHYDE PRODUCT AND AQUEOUS ACID SOLUTION FROM SAID CATALYST REMOVAL ZONE TO A FIRST SETTLING ZONE, WITHDRAWING AN ALDEHYDE PRODUCT SUBSTANTIALLY REDUCED IN COBALT FROM SAID SETTLING ZONE, PASSING SAID ALDEHYDE PRODUCT TO A HEATING ZONE, PASSING LIQUID WATER TO SAID HEATING ZONE, MAINTAINING A TEMPERATURE OF FROM ABOUT 250-350* F. IN SAID HEATING ZONE, PASSING ALDEHYDE PRODUCT AND AN AQUEOUS PHASE FROM SAID HEATING ZONE TO A SECOND SETTLING ZONE, AND WITHDRAWING A ALDEHYDE PRODUCT SUBSTANTIALLY COMPLETELY FREE FROM DISSOLVED COBALT FROM SAID SECOND SETTLING ZONE. 